Heterotaxy Syndrome

Treating heterotaxy can be extremely complicated, given the number of organs involved and the presence of multiple congenital heart defects. Some children with heterotaxy syndrome, for example, are born with only one ventricle. 

Another common feature of heterotaxy syndrome is the absence of a spleen, the existence of multiple, smaller spleens or a spleen that does not function effectively. Because the spleen plays an important role in fighting infection, an absent or malfunctioning spleen can make it harder for patients to recover from surgery or fight infections.

In healthy bodies, the right side and the left side are not identical. Likewise, organs that occur in pairs, such as the lungs, are not the same. In heterotaxy syndrome, however, dual organs are mirror images of each other—a trait that is known as isomerism. 

There are two types of heterotaxy syndrome:

• Right isomerism is accompanied by several heart defects, typically involving major structures such as the septa (the walls dividing the heart) and the valves, which regulate the flow of blood between the chambers of the heart. There may be irregularities in blood flow returning from the lungs. In right atrial isomerism, the spleen may be missing from the body.
• Left isomerism also involves defects of the septa and valves. The heart’s electrical system may not work correctly. Because the electrical system plays an important role in timing the heartbeat and the coordinated pumping of the heart’s chambers, this can cause serious problems. Some children may experience heart block, which means the electrical systems of the upper and lower chambers (the atria and the ventricles) cannot communicate or receive electrical signals. This problem can be corrected with a pacemaker. In left atrial isomerism, there may be several smaller spleens. Left isomerism also frequently involves an abnormality in the large vein returning to the heart from below the diaphragm—an interrupted inferior vena cava.

The exact cause of heterotaxy is not known. One theory is that it results from a failure of the axes of the fetus to rotate properly during pregnancy. 

Symptoms of Heterotaxy Syndrome

Each occurrence of heterotaxy is unique, and symptoms may vary depending on which organs are affected. Children with right atrial isomerism begin to show symptoms shortly after birth due to defects in the critical structures of the heart. Labored breathing, difficulty with feeding, lack of energy and cyanosis (blue lips, nails, or skin) may be noticeable. Children with left atrial isomerism may be asymptomatic until later in childhood and even into adulthood. 

Diagnosis of Heterotaxy Syndrome

Heterotaxy syndrome can be diagnosed before or after birth. Due to its many structural abnormalities, heterotaxy is often diagnosed with a fetal echocardiogram during pregnancy. This form of ultrasound captures detailed pictures of a baby’s heart while it is still in the womb.

Diagnostic testing after a baby is born can include chest x-rays and a detailed form of ultrasound known as an echocardiogram. A cardiac MRI provides another way to view the heart’s structural abnormalities. Since heterotaxy can involve disruption of the heart’s electrical system, an electrocardiogram, which measures the electrical activity of the heart, can be a useful diagnostic tool.